The best metal seed backup is not the one with the most dramatic fire claim. It is the simplest device that keeps every mark legible after heat, corrosion and crushing—and that you can fill in correctly without exposing the phrase.
We do not make or sell backup products. Some links may earn a commission. Availability and published prices were checked in August 2026. Manufacturer claims are identified as claims; independent stress-test results are kept separate.
The picks
| Pick | Published price | Format | Verdict |
|---|---|---|---|
| Blockplate 24 | $79, but sold out when checked | 3 mm 304 steel, center-punched grid | Best proven simple design if stock returns |
| Coinplate Alpha | €85, but sold out when checked | Two 5 mm 304 steel plates, center-punched | Best heavy flat enclosure |
| Cryptosteel Capsule / Seed24 | Seed24 from roughly $70 during the checked sale | Character tiles inside a steel capsule | Best protected tile design; more moving pieces |
| Keystone Tablet Plus | $69 | 304 steel letter tiles | Easy to assemble, but an older independent test scored heat survival poorly |
| DIY punched plate or washers | Usually the cost of steel plus tools | Stamped or center-punched 304/316 steel | Best value if you practise first |
There is no winner you should buy at any price. Independent tester Jameson Lopp has tested 75 designs and concludes that simple single plates with center-punched grids are generally the best value. Many inexpensive plates received straight A grades. Several elaborate tile devices did not.
Best design: a thick, center-punched plate
A grid plate has almost nothing to fail. You mark the first four letters of each BIP-39 word with an automatic center punch. Heat can discolour the surface and crush can bend it, but a deep indentation remains readable. There are no loose tiles, rails, screws or springs that must keep their order.
Blockplate 24 is the clearest commercial example: 11-gauge (3 mm) 304 stainless steel, 24 words over two sides, with adhesive positioning guides. It received A grades for heat, corrosion and crush in Lopp’s test. Its problem in August 2026 was not engineering; it was availability.
Coinplate Alpha takes the same principle to an extreme: two 5 mm plates bolt together around the markings. The complete unit weighs about 1.1 kg. It also received straight A grades. That mass is reassuring in a building collapse and inconvenient in a safe-deposit envelope. Buy the engineering you need, not the heaviest object in the category.
Best capsule: Cryptosteel, with an important testing caveat
Cryptosteel stores letter tiles and separators on a core inside a threaded steel shell. The original Capsule uses AISI 303 and 304 stainless steel. A commissioned university furnace test found the data readable after exposures from 1,100 °C through 1,350 °C; above 1,100 °C the capsule had to be cut open, and at 1,400 °C it melted.
That is unusually specific evidence. The caveat is equally specific: the laboratory tested the original Capsule construction. Cryptosteel says newer Seed12 and Seed24 products use the same materials and rates them similarly, but “same steel” is not the same as an independent test of the complete new assembly.
The tile format is quick to build and protected from direct flame. It also has hundreds of pieces and relies on separators retaining order. Lopp’s older Capsule test earned A for heat and corrosion but B for crushing. Choose it because you need a compact protected tile system, not because 1,400 °C is a magic number.
Keystone Tablet Plus: convenient, not our durability pick
Keystone’s $69 Tablet Plus is made from 304 stainless steel and gives every letter tile its own slot. It is fast, reusable and supports 12, 18 or 24 words. The official materials page says it resists fire, water and corrosion.
Independent testing is the reason it does not rank higher here. Lopp’s published table gives the Tablet Plus an overall C: A for corrosion and crush, F for heat. A material can be heat-resistant while the assembled data-retention design fails. Product selection should follow the tested assembly, not just the alloy name.
The honest value pick: make a simple one
A piece of 304 or 316 stainless steel, an automatic center punch or hardened letter stamps, numbered rows and an hour of careful work can perform as well as a branded product. The physics does not recognise logos. Lopp’s table gives A grades to multiple DIY designs costing around $20–$50.
- Practise every character on scrap from the same material.
- Copy the phrase to paper and verify it before touching the metal.
- Mark word numbers first.
- Work somewhere without cameras, windows or visitors.
- Read the completed backup back into a blank numbered template.
- Use the wallet’s official backup check before destroying the temporary paper.
What matters more than the brand
- Deep marks. Surface ink and shallow laser colour are not recovery data.
- Retained order. A pile of correct tiles in unknown order is a failed backup.
- Ordinary decoding. An heir should not need a vanished app or private website to read the plate.
- Separate secrets. Never put the passphrase on the same object as the seed.
- Two locations. Metal resists a fire; it does not resist theft, confiscation or inaccessible premises.
- A tested restore. A perfectly engineered plate with one wrong mark preserves the mistake for centuries.
Who should buy none of these
If the amount is small and temporary, two carefully written paper copies in dry, separate places can be proportionate. Metal mainly improves durability. It does not fix phishing, a bad passphrase, an untested backup or an heir who does not know the object exists.
For the storage plan around the plate, read how to store a seed phrase. For materials and formats rather than products, see what metal backups survive.
Sources checked
- Jameson Lopp’s independent heat, corrosion and crush-test table
- Blockplate 24 specifications and availability
- Coinplate Alpha specifications and availability
- Wrocław University laboratory report for the original Cryptosteel Capsule
- Cryptosteel materials and temperature claims
- Keystone Tablet Plus specifications and price
Get the SteelPhrase Self-Custody Brief
Email me SteelPhrase about twice a month: security changes, practical checklists, and carefully reviewed wallet guides. Unsubscribe anytime.